Apparatus for measuring the stiffness of flexible materials



April 5, 1938 G s n- 2,113,389

" APPARATUS FOR MEASURING ;IHE STIFFNESS OF FLEXIBLE MATERIALS Filed May 51, 1932 4 Shets-Sheet 1 April 5, 1938. $M|TH 2,113,389

APPARATUS FOR MEASURING THE STIFFNESS .OF FLEXIBLE MATERIALS Filed May 51, 1952 4 Sheets-Sheet? April 5, 1938. G. H. SMITH 2,113,389

APPARATUS FOR MEASURING THE STIFFNESS OF FLEXIBLE MATERIALS Filed May 51, 1932 fSheets-Sheet a Inna-"e April 5, 1938.

G. H. SMITH APPARATUS FOR MEASURING THE STIFFNESS 'OF FLEXIBLE MATERIALS Filed May 51, 1932 4 Sheets-Sheet 4 a n H1 7 y 7\ m Patented Apr. 5, 1938 PATENT OFFICE APPARATUS FOR MEASURING THE STIFF- NESS F FLEXIBLE MATERIALS George H. Smith, Kenmore, N. Y., assignor to Ralph F. Taber, North Tonawanda, N. Y

Application May'31, 1932, Serial No. 614,517 7 Claims. (01. ass-1"!) ent materials such as paper, cloth, threads, wires and sheet metal,- by bending or flexing a strip of given size througha given angle or a given amount and the force required to produce the given fiexure is indicated as an index of the 10 stiffness.

An object of the invention is to provide in such apparatus, a holder for the test strip, a pointer operatively associated with the holder, means for restricting relative movement'of the 15 pointer and holder, and scales reading to the right and to the left of the normal or rectilinear position of the test strip, whereby the test strip may be bent first to the right andthen to the left and readings taken when the strip is deflected to its limit in each direction, so that an average may be computed from the aggregate scale readings to-accuratelydetermine the stiffness index of the material. v

A further object is to provide apparatus including a. pivoted pointer adapted to engage one end of the test strip, a yieldable holder for clamping the opposite end of the test strip, the pointer being manually movable across the scale to the position where the test strip disengages from 30 the pointer and snaps back to the rectilinear, and means for retaining the pointer deflected at such point so that the scale reading may be readily observed.

A further object is to provide means for increasing the range of the instrument accordin to the type of material to be tested.

A further object is to provide a cutter by means of which the test strips may be cut to a predetermined exact length and width.

40 With the above and other objects in view the invention consists in certain novel details of construction and combinations of parts hereinafter fully described and claimed' it being understood that various modifications may be resorted to 45 within the scope of the appended claims without departing from the spirit or sacrificing any of the advantages of the invention.

In the accompanying drawings forming part of this specification,

50 Figure 1 is a perspective view of one form of the apparatus,

Figure 2 is a cross section taken on the line 2- -2 of Figure 1,

Figure 3 is a vertical central section of the 55' app ratus.

Figure 4 is a detail front elevation of the pendulum,

' Figure 5 is a detail section showing the method of increasing the range of the instrument,

Figure 6 is a front elevation of a modified 5 form of the invention,

Figure 'Iis an end elevation of the instrument shown in Figure 6,

Figure 8 is a front elevation of another modified form of the invention, v

Figure 9 is a detail cross section taken on the lineS-S of Figure 8,

Figure 10 'is a plan view of another modified form of the invention, and,

Figure 11 is a cross section taken on the line 15 ll-ll of Figure 10'.

In order to measure the stifiness ofmaterials it is desirable but not necessary to arrange a test strip in vertical position and to take account of the weight of the strip, making compensation for the amount oi. bending or flexing caused by its own weight. It is further desirable to limit the flexing of the strip to an amount less than the elastic limit of the material being tested as stiffness cannot be measured at or beyond the '25 elastic limit in view of the difference between the quality of a material which imparts stiffness as compared with its elastic qualities.

The invention is therefore adapted to register the stiffness of materials when flexed a limited and fixed amount by a known force with a given 'size of strip for testing. The term strip as herein used is to be interpreted to mean a,test strip of given length and width as well as a thread, wire or other piece of material of a given size capable 5 of being tested.

It is well known that paper, for instance, is stiffer on one side than on the other, that is, it may exhibit greater stiffness, when bent to. the right than when bent to the left, or vice 40 versa. This is attributed to the greater density of fibers on the "wire side of the papersheet. To obtain the accurate stifiness index of paper, the present tester is provided with spaced scales having their origins adjacent to the normal, vertical or unstressed position of the test strip so that the test strip may be bent either'toward or away from the wire side without removing the test strip from the holder by simply reversing the direction of movement of.the pointer, and thereupon the aggregate readings of both scales may be averaged to obtain the stiffness index.

Referring now to the drawings in which like characters of reference designate similar parts in the various views, ll designates a frame and II a,

base'from which the frame extends perpendicularly, both these parts preferably being formed of metal cast in one piece, or may be formed' of other materials and assembled as desired. Preferably the frame is closed at the back by a back plate l2, as shown in Figure 3, and is closed at the front by a dial IS, the base edge of the frame being-substantially straight and provided with a recess i4 to receive the bottom straight/edge portion of the dial. The back plate I2 is provided with a hub I5 which extends through an opening IS in the dial. Preferably the frame is arched in a general way in contour, as best shown in Figure 1, and the dial may be removably secured thereto by screws [1.

The base, as best shown in Figure 3, comprises a flat table top I 8 having a marginal flange l9 extending therearound and supporting the 'apparatus level upon a desk, table, or other suitable support and preferably felt or similar buttons 20 are arranged at the corners of the flange to prevent marring of the furniture.

Referring again to Figure 3 it will be seen that a shaft 2| is mounted in the hub ll. The shaft is uniformly enlarged at the outer end to provide a bearing 22. .Beyond the bearing, the shaft is again enlarged to provide a head 23 and beyond the head the shaft is uniformly reduced to provide an abutment 24. The shaft issecured in place by means of a nut which engages the back plate l2 and coacts with a shoulder 25 on the bearing 22, which engages the front end of the hu; I, to hold the shaft against rotation in the hu A pointer 28 is provided centrally with an opening 21 which is equipped with a fiber bushing 22 to frictionally fit the bearing 22. Below the bushing the pointer is split, as shown at 29. The bushingis preferably split so as to be contracted and driven shugly into the opening 2! and it will be seen that the head 23 of the shaft engages the front edge of thebushing and holds the rear edge of the bushing against the front end of the hub II to removably mount the pointer on the shaft.

The top of the pointer is slotted to receive a plate it which extends forwardly at a right angle to the pointer and forms a grip which may be grasped by the thumb and forefinger of the operators hand to swing the pointer on the shaft either to the right or to the left. The plate is secured to the pointer by means of spaced rivets ll orotherwise. The plate proiectsbeyond the pointerat the rear edge and terminates in a finger 32 which constitutes the tip of the pointer. The bottom edge of the plate beyond the pointer 28 is extended downwardly to provide a stop ing 33. When the pointer is swung to the right or to the left on the bearing 22, by virtue of the bushing 28 engaging the bearing 22 with considerable" friction, the pointer will remain at its limit of movement in either direction.

The pendulum 34 is substantially rectangular both inlongitudinal andcross section and is provided near the top with a mounting opening 35. To mount the pendulum a screw 3 is threaded into the end of the shaft 2|. The screw is provided intermediate the ends with a standard ball bearing assembly, the outer race 31- of which is press fitted into the mounting opening 35 of the pendulum, while the inner-race 38 is removably clamped between the shoulder as of an enlarged neck 40 on the screw and the above mentioned abutment 24 on the end of the shaft 2 l.

' .The'pendulum is provided witha slot 42 in the top to receive the lower end of test strip 43.

,ing to the direction of movement of the 'frame II and is for; the purpose of multiplying the effective weight of the pendulum and increasing the range of the instrument, as will hereinafter be described'in detail.

By referring now to Figure 1, it will be seen that the specimen strip 49 to be tested is inserted at the bottom in the holder of the pendulum and the set screw 45 tightened. I'he strip is of sufficient length to extend slightly beyond the stop lug 33 of the pointer and lodge thereagainst so that when the grip 30 is moved slowly across the dial the test strip will be deflected from the vertical and bent to the right or to the left accordriointer. Each side of thedial to the right and left of the vertical axis thereof is provided with a scale 50, both scales being counterparts of each other and calibrated in any desired units.

When the pointer is moved slowly across the scale to the position where the strip snaps back to'vertical the scale is read at that point. Then the strip is bent in the reverse direction in the same manner and, the reading on the opposite scalenoted. The'average of the right and left scale readings is the stiflness index of the speci-. men. when the strip snaps past the stop lug it has been flexed to a given extent and the scale reading. at the point of the srfapping of the strip. past the stop lug therefore registers the stiffness of the material. This applies to each of the forms of the invention disclosed.

Preferably the test strips are cut to exact length and widthrsay for instance, 1.5" by 3.5. For this purpose a pair of guide strips 51 and 5: are secured to tlie flat top l8 of the base, as best shownin Figures 1 and 2. A knife 53 is pivoted at the rear end on a pivot pin 54 secured to the frame N, as best shown in Figure 3 and is held against a shear strip 55, best shown in Figure 2, by means of a flat leaf spring 56 held in place at the rear end by the pivot pin 54 and having the free'end forked, as'shown at 51 in Figure l, to receive a lateral pin 58 carried by the knife. The test strip may be cut to the exact width by being passed from the front toward the rear of the base against the guide strip 52, as shown in Figure 2. The test strip may be cut to the exact length by being inserted endwis'e underneath'the knife on the table top until it engages the guide strip 5l, as shown in Figure 1. I

The multi-range weight 41 is inserted in one of the 'openings 46 in the pendulum to multiply the effective weight of the pendulum. The range factor is stamped on the head of the weight and 'the scale reading is multiplied by this number.

For instance, if the reading is 47 on the scale and a weight having a factor of two stamped on its head is used, then the stiffness is twice 47 or 94. Inall caseswhere a double, right and left, scale instrument is used, test specimens are bent both ways and the average of the right 'and left scale represents the stiffness of the specimen. Thus a strip test, for example maybe as follows. Left scale reading 47x2 (weig factor) equals ninetyfour, right scale reading 42x2 (weight factor) angle of approximately twenty-two and one-half degrees. At this limit of flexing the 'end f the test strip will snap past stop-lug 33 so that this snap action prevents flexing of the test strip beyond a given angle or given amount that is predetermined sothat all test specimens are flexed the same given amount in testing in order that the scale readings may be subsequently com.- pared. Therefore, reference made herein and in the claims to means limiting the flexing of the test strip to a given amount shall be interpreted to include the parts hereinabove described cooperating in the manner described so that the flexing of the test strip will not exceed the elasti limit as hereinbefore stated.

In the above described form of the invention the pointer bends the test strip until the pull of the pendulum causes the strip to snap past the stop plate. A modified form of the invention is shown in Figuresfi and 7 in which a weight and a cam lever is substituted for the pendulum, the cam lever being so shaped as to give a uniformly increasing pull to the weight which permits of the graduations on the scale being all the same distance apart in contrast to the pendulum de-' sign wherein the decreasing pull of the pendulum ,in proportion to the distance moved must be compensated. for by increasing the size of the graduations.

Referring to Figure 6 it will be seen that upon a base 59 there is mounted an upright dial to having an arcuate scale 6| disposed thereon.

Upon a pivot pin 62- there is mounted a pointer 63 which may be identical in construction with the pointer 26, above described in detail. Also mounted upon thepivotpin is a cam 64 having a fiat side 65 and a curved cam surface which gradually increases in radius from one end of the fiat side to the opposite end of the'flat side, as shown. A weight 61 is suspended from the cam by a cable 68 and serves to balance the assembled cam and pointer so that the pointer and the fiat side of the cam normally extends horizontally.

The test strip 69 is clamped in a holder in e cam produced by slotting the cam surface, as shown at 10, to receive one end of the strip, a set screw "II being urged against a clamp strip 12 in the slot to clamp the strip in the slot, The strip is of sufficient length to overlap stop projection 13 on the grip ll of the pointer. As the pointer is moved slowly/around the scale G-l by manual pressure against the grip II the cam exrts an increasing opposition to mpvementof the pointer until the test strip 69 snaps of! the stop projection I3 and springs back to the rectilinear position. The pointer will remain deflected to its limit of movement and indicate on the scale the degree of rigidity of the particular specimen strip being tested. a

Another modified form of the invention is shown in Figures 8 and 9 in which a helical spring is employed to retard movementof the test strip holder relative to the pointer instead of a pendu- "II. A stationary pivot pin 18 projects from the front face of the dial 16. A pointer 1-9, similar to the pointers above described, is mounted to turn. on the pivot pin and is friction retarded bya bushingtll to remain at its limit of deflected movement, as also above described.

In this embodiment of the invention the strip holder 8| is substantially oblong in cross section and contour andv is rotatably mounted on the pivot pin. The holder is equipped in one end with a slot 82 toreceive the test strip 83, which latter is clamped in the slot by means of a clamp strip 84 urged against the test strip by means of a set screw 85. The test strip is of sumcient i may be taken to length to overlap the stopiproiection 13 of the pointer.

A coil spring 86 is mounted on the pivot pin Between the pointer and the strip'holder, one end of the spring being secured to the pivot pin by means of a pin 81, and the outer end being secured to the holder 8| opposite .the slot 82 by means of a pin 88. g

In operation the pointer is manually moved over the scale, as above described, to bend the strip. The spring exerts a gradually increasingpull on the holder so that eventually the test strip will snap past the stop projection 13 and return to the rectilinear, the pointer remaining at its limit of deflection so that the scale reading determine the degree of rigidity of the test' strip.

Various sizes of springs or dial combinations may be used in the modified form, shown in Figure 8, to vary the range of the instrument. In the modified form, shown in Figure 6, various weights 89 may be mounted on thefiat face of the cam on the opposite side of the pivot pin from the weight 81 to obtain the. same result. Such, weights may be provided with a stem 90 which is slidably fitted in a groove 9| on the flat faceof the cam to accommodate adjustment of the weight longitudinally of the cam toward and away from the pivot pin 62.

Another modified form of the invention" is shown in Figures ,10 and 11 in which the instrument is adapted'to be laid flat on a desk or similar support and preseht its dial horizontally.

Referring now to Figure 10 it will be seen that a substantially circular base or casing 92 is closed at the bottom by a base plate 93 which is pro,- vided centrally with a ball bearing .assembly 94 mounted in a cup 95 disposed centrally on the base plate. An upright pivot pin 96 is fixed at the bottom in the inner face of the ball bearing assembly and thus may turn on its axis. A coil spring 91 is secured at the outer end to the wall of the casing by'means of a screw 98,:an'd is secured at the inner end to the pivot pin by means a neck II! which frictionally engages in a flange 106 formed in the top of the casing 92 so tli at the, pointer will be retarded in its movement by such frictional engagement. A ball bearing assembly IE1 is mounted in the bore )8 of the annular neck Hi5 and encircles the pivot pin. The ball bearing assembly I01 permits of the pivot pin freely turning on its axis within the collar IN; The pointer is provided with an upstanding stop projection I for detachably engaging the test, strip Ill.

The holder for the test strip comprises ablock A il I having a slot II! to receive the testistrip, a clamp strip Ill being urged by a set screw Ill to bind the test strip against the wall of the slot, as heretofore described. By referring to Figure 11 it will be seen that the pivot pin 88 is provided with a reduced threaded terminal I I 5. Upon this terminal the holder .III is mounted by means of .a screw Iii provided with an interiorly threaded shanki I 1 that receives the threaded terminal, a

suitable opening H8 being formed in the holder to receive the head and shank of the -screw.

7 When the screw is tightened upon the terminal I IS the holder will be clamped against a shoulder ll! formed at the base of the terminal I Wand "secured for movement as a unit with the pivot shaft 96.

The top surface ofthe casing 92 is preferably equipped with spaced scales I20 having their origlns at the .rectilinear position of the test strip,

as-best shown in Figure 10, so that in this form of the invention thetest strip may be bent bothto the right and to the left by corresponding movement of the pointer, the holder being, meanwhile, retarded in its movement by the spring 91, until the, pull of the spring 'oauses the test strip to snap past the stop projection" I09 and return to the rectillnear, as above described. The pointer remains at its limit of deflected movement due to the frictional engagement between the annular neck I05 and flange I 06 so that the scale I readings may be taken and averaged to co inpute test strip of flexible material including, a holder adapted to clamp one end of'the test strip, a pointer adapted to releasably engage the free end of the test strip, a common pivot for the holder and. the pointer, a scalehaving its origin I adjacent to the normal or unstressed position of the test strip, ,means for retarding movement of the holder relative to the pointer, said pointer being manually movable, across the scale to bend the test strip until it snaps back to the normal or unstressed position, and means for holding the pointer in its deflected position after release of the strip so that the scale reading may .be taken. v

2. Apparatus for measuring the stiffness of -a teststrip of flexible material including, a movable holder adapted to clamp one end of a test strip, a pivotedmointer adapted to releasablyengage the free end of the test strip, a dial 'provided with spaced scales graduated to the right and left respectively of the normal or unstressed position of the test strip, means for'retarding movement of the holder relative to the pointer, said strip being adapted to be bent to the right and to the left in sequence by manual movement of the pointer overthe scales until released by the pointer, and means for holding the pointer in its extreme deflected position so that readings may be taken when the strip is deflectedprojection adapted to overlap and releasably engage one end of, the material, a holder on the pendulum above said pivot adapted to grip the other end of the material, a dial, and scales on the dial disposed laterally of the normal or unstressed position of the pendulum, the pointer being adapted to be moved manually across. the scales by said grip to bend the material in sequence to the right and to the left until the material disengages from said projection at the end of each movement, said friction means holding said pointer stationary at the moment of disengagement of said material to permit the scale reading underneath the pointer being taken. I

4. Apparatus for measuring the stiffness of a test stripof flexible material including, apivoted pointer adapted to overlap and releasably engage one end of the test strip, a holder having terminal means for clamping the other end of the-test strip, a cam and weight operatively connected to the holder and retarding movement of the holder relative to the pointer, move ment of the pointer transmitting movement to the holder through the test strip, a scalevpositioned laterally of the -normal orlunstressed position of thetest strip and'havlng its origin at said position, and means for frictionally retarding movement of the pointer adapted to hold the'izinter at deflected positions.

5,1 pparatus for measuring. the stillness of a test strip of flexible material including,.a pivoted pointer adapted to overlap and releasably engage ,one end of the test strip, a holder ,hav-

ing terminal means. for clamping the other end,

of the test stripfa common pivot for the pointer and the holder, a cam flxed 'to the holder, a weight suspended from the cam, said cam and weight exerting increasing pullyonthe holder during'pivotal movement thereof, said pointer being manually pivoted and pivoting the holder through the instrumentality of the test strip whereby the test strip .is'ben from its normal or unstressed 'condltion,'and a sale having its origin at said normal or unstressed position of the strip and traversed by the pointer.

6. An apparatus for measuring the stiffness of V a, test strip of flexible material including, a ,pointer, a holder," a stationary pivot for the pointer and the holder, a grip for moving the pointer having a projection adapted to overlap and releasably engage-one end'of the test strip, a clamp on the holder for gripping the other end of the test "stripgia spring secured at one end of the site end to :the holder ,for retarding movement of the holder/and-ia scale positioned laterally'of the normal or unstressed position of the test strip, thepointer being adapted to be moved manually across the scaleby said grip to bend the test strip until the pull of the spring on the holder causes the test strip to snap past said projection and return to the normal or unstressed condition, the scale reading underneath the pointer at the deflectedposition of the pointer indicating the stifiness index of the test strip.

by the holder for clamping one end 01' the test strip, means carried by thepointer for releasably engaging the other end of the test strip, relative movement of the .pointer and holder bending the test strip, means for retarding the holder to exert increasing pull upon the test strip until it snaps oil of the pointer; means'for frictionally holding the pointer at deflected positions, and a scale traversed by the pointer and having its origin at the normal or unstressed position of the test strip.

' GEORGE E. SMITH. 

